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Geothermal & Oil Fired Boiler

jasonmm
jasonmm Member Posts: 10
Friends,

I currently have a Burnham V7 Oil Boiler installed in 1996 with 5 zones. It is working well.

Is there a Heat Pump system that could be made the primary heat source with the oil boiler backing it up?

Comments

  • Hot_water_fan
    Hot_water_fan Member Posts: 1,004
    edited November 2022
    Yes - an air-source or ground-source system would both work. Both have pros and cons, so it'll depend on your situation. The Caleffi Idronics journal is a great resource for something like this.

    5 zones - What type of zones are these? In-floor heating, baseboard, radiators, etc.?

    In_New_England
  • pecmsg
    pecmsg Member Posts: 3,536
    Ground source unit that can heat water over 120 - 130*F ?
  • jasonmm
    jasonmm Member Posts: 10
    4 are baseboard heating and one is in-floor for a bathroom & shower.
    Hot_water_fan
  • pecmsg
    pecmsg Member Posts: 3,536
    You might be able to do the in floor but baseboard highly doubtful. 
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,004
    edited November 2022
    Depends on the baseboard amount/rype and the heat loss, and there are water-to-water heat pumps that take you up to 160. Regardless, the oil boiler is there to cover the shortfall - think the 80/20 rule. 

    Does this home have AC?
  • jasonmm
    jasonmm Member Posts: 10
    Yes, the AC is an attic mounted system with the duct work all in the attic. The outside unit is a typical central air installed in 2012.
    Hot_water_fan
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,004
    Yes, the AC is an attic mounted system with the duct work all in the attic. The outside unit is a typical central air installed in 2012.


    Gotcha - an air-to-water/water-to-water heat pump could also use the ductwork for cooling (even heating if needed). Or you could replace the existing AC with a heat pump, which would probably be the cheapest and easiest switch, but your baseboard would then be used a lot less.
    In_New_England
  • jasonmm
    jasonmm Member Posts: 10
    First step we are taking is getting the attic sealed and insulated soon so that the oil boiler doesn't have to run so often.

    When I bought the house last summer I was very surprised to find out I have about R-20 in the attic. I live in Wisconsin where I've seen it recommended to have R-49!!!

    Once that gets taken care of I'm really interested in doing a heat pump of some kind.
    Hot_water_fan
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,004
    How much oil did you use last winter? 
  • jasonmm
    jasonmm Member Posts: 10
    A 275 gallon tank a month in the cold months. I had 4 tank fills approx 1,000 gallons @ $3.20 a gallon = $3,200. Holy Moly!

    My first fill in Wisconsin this year was $3.84 cents a gallon at the beginning of October.
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,004
    Ouch! Pretty easy to beat oil at those prices, even if oil is much higher elsewhere. A hybrid setup like you're considering is a strong choice, it gives you a lot more options since electricity can be generated with many sources.
  • pecmsg
    pecmsg Member Posts: 3,536
    Air to air heat pumps for 75 - 80% of the winter. Oil for the coldest nights. 
  • In_New_England
    In_New_England Member Posts: 130
    jasonmm said:

    A 275 gallon tank a month in the cold months. I had 4 tank fills approx 1,000 gallons @ $3.20 a gallon = $3,200. Holy Moly!

    My first fill in Wisconsin this year was $3.84 cents a gallon at the beginning of October.

    How large is your home? I'm near Boston in a 1400 sq ft heated space and we use 600-700 gallons of oil per year.

    I'm also looking at what can be used as an 80/20 solution over the oil heat.
  • jasonmm
    jasonmm Member Posts: 10
    @In_New_England My house is 2400 Sqft with too little insulation. I am having a company seal my attic and increase my insulation from around an R-20 to R-49 in a few weeks so that should greatly help keep my bills down.

    After that I'm looking to do solar panels connected to a battery system for my well pump. Then I'll look into the Heat pump. The reason I asked about geothermal was because I have 4 acres and could dig a few trenches for it.
    In_New_England
  • jasonmm
    jasonmm Member Posts: 10
    @Hot_water_fan I tried looking at the Caleffi Idronics journal but that isn't for lay people like myself. Is there something more specific I could search for? Thank you
  • pecmsg
    pecmsg Member Posts: 3,536
    jasonmm said:

    @In_New_England My house is 2400 Sqft with too little insulation. I am having a company seal my attic and increase my insulation from around an R-20 to R-49 in a few weeks so that should greatly help keep my bills down.

    After that I'm looking to do solar panels connected to a battery system for my well pump. Then I'll look into the Heat pump. The reason I asked about geothermal was because I have 4 acres and could dig a few trenches for it.

    How deep to get to water?

    Rocky or sandy soil?

    You won't be able to Start that compressor on solar. Continue running possibly.
  • jasonmm
    jasonmm Member Posts: 10
    @pecmsg I hope it would start with 7300 watts and 30 amps. :-) All pumps would run off the batteries and hopefully the solar would be enough to top them off each day. If it is too cloudy then I'd have to run a 6000-watt generator for 2 hours to recharge up to 12 kwh.

    I figure the commodities that will become scarce in an emergency are gasoline and diesel. My idea is to only run the generator on propane 2 hours a day at most to stretch out any fuel that is available.

    Defiantly not looking to get a return on investment from the batteries / solar though. Just in case...
  • Jamie Hall
    Jamie Hall Member Posts: 20,425
    Depends on the heat pump -- but any pump big enough to be useful in your house is going to require at least a 50 amp 240 volt fuse or breaker. And true sine wave power. As @pecmsg said, there is a chance it might keep running on 30 amps 240 volt power -- but I wouldn't count on it.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • jasonmm
    jasonmm Member Posts: 10
    @Jamie Hall wow that is good to know. Thank you.
  • WMno57
    WMno57 Member Posts: 663
    I agree with @pecmsg that starting a compressor with solar and batteries will be difficult. The reason is starting amps are much higher than running amps for an electric motor under load. Also true for your well pump. I do have a solution for you for the well. This system has been in place at an off-grid cabin for 13 years. The cabin is north of you in Michigan's upper peninsula. The well pump is a special soft start 120 volt well pump. Here is the cabin owners blog where he describes in great detail his battery bank v1.0 and 2.0.
    https://offgridcabin.wordpress.com/
  • pecmsg
    pecmsg Member Posts: 3,536
    edited November 2022
    Rather than chance the starting and running issues during an emergency your better off with a oil or gas furnace that uses a lot less power. 
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,004
    @In_New_England My house is 2400 Sqft with too little insulation. I am having a company seal my attic and increase my insulation from around an R-20 to R-49 in a few weeks so that should greatly help keep my bills down.


    Replacing R-20 with R-49 will decrease your energy bills, but definitely not economically. Diminishing returns with insulation. Cheaper to just buy electricity or oil.
    pecmsg
  • pecmsg
    pecmsg Member Posts: 3,536
    edited November 2022
    Replacing R-20 with R-49 will decrease your energy bills, but definitely not economically. Diminishing returns with insulation. Cheaper to just buy electricity or oil.
    I disagree. Tightening the envelope gives a return on investment year after year with no add on costs.  
    Oil and gas will continue to go up. 
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,004
    edited November 2022
    @Hot_water_fan I tried looking at the Caleffi Idronics journal but that isn't for lay people like myself. Is there something more specific I could search for? Thank you


    Air-to-water/water-to-water conversions are pretty technical and niche, there's a lot to balance. You have a few options here:
    1. Replace the AC with a heat pump. You'd use the ducts for forced hot air and if you need, the boiler/electric resistance for backup. The cheapest and possibly the most efficient. This can be combined with the other 2 options.

    2. Add an air-to-water heat pump to use the baseboard. Air-to-water units produce lower max temperatures than oil boilers. If your baseboard is sized for high temp water (around 600 btu/linear feet of baseboard), you'll have a shortage. How many linear feet do you have? And what part of Wisconsin?
    2A. You can use the oil boiler as backup.
    2B. You can reduce the temperature needed through more insulation and air sealing. But it can't just be the attic, the BTUs/LNFT needs to be low enough for a heat pump in every room
    2C. You can reduce the temperature needed through more radiation.
    2D. You can use the ductwork to supplement the baseboard.
    2E. You can raise the water temp with a water-to-water heat pump, using the air-to-water to
    preheat the water. This uses a different refrigerant.
    2F. You can combine many of these options to get you there. That's why the Idronics is helpful,
    there's a lot of details.

    3. Add an water-to-water (commonly called geothermal) heat pump to use the baseboard. These units produce lower max temperatures than oil boilers. If your baseboard is sized for high temp water (around 600 btu/linear feet of baseboard), you'll have a shortage.
    3A. You can use the oil boiler as backup.
    3B. You can reduce the temperature needed through more insulation and air sealing. But it can't just
    be the attic, the BTUs/LNFT needs to be low enough for a heat pump in every room.
    3C. You can reduce the temperature needed through more radiation.
    3D You can use the ductwork to supplement the baseboard.
    3E. You can raise the water temp with another water-to-water heat pump. This uses a different
    refrigerant.
    3F. You can combine many of these options to get you there.
  • WMno57
    WMno57 Member Posts: 663
    edited November 2022
    pecmsg said:

    Oil and gas will continue to go up.

    My crystal ball (thanks @clamb) says oil will be 70 cents per gallon cheaper one year from today.
    https://www.barchart.com/futures/quotes/HOM11/futures-prices
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,004
    edited November 2022
    I disagree. Tightening the envelope gives a return on investment year after year with no add on costs.


    Not necessarily a positive return on investment as these projects are not free. Say you save 4,250 btu/year/sqft in the attic, which is pretty reasonable from R-20 to R-49. That's only a discounted 65,000 btu at 30 years and 5%. If that costs you $3/sqft, that's about $5/gallon oil. Hard to swing that.
  • pecmsg
    pecmsg Member Posts: 3,536
    I don’t see those #’s adding up. Care to show me the math.
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,004
    edited November 2022
    @pecmsg of course! Not a problem. Focusing on an attic, since that’s easiest. 

    R-20: 6000HDD/year x 24(hrs/day)/20 (R-value)= 7200btu/sqft/year.
    R-49: 6000HDD x 24 /49 = 2939btu/sqft/year. 

    Difference of 4260 btu/year. Over 30 years with a 5% interest rate, that’s the same as saving 65,000 upfront (with an infinite timeline, that’s 4260/.05 = 85,000btu).  If it costs $3/sqft, that’s $46 per MMBtu, or about $5/gallon with a 80% boiler. Lots of assumptions here of course, but you get the gist. 
  • pecmsg
    pecmsg Member Posts: 3,536

    @pecmsg of course! Not a problem. Focusing on an attic, since that’s easiest. 


    R-20: 6000HDD/year x 24(hrs/day)/20 (R-value)= 7200btu/sqft/year.
    R-49: 6000HDD x 24 /49 = 2939btu/sqft/year. 

    Difference of 4260 btu/year. Over 30 years with a 5% interest rate, that’s the same as saving 65,000 upfront (with an infinite timeline, that’s 4260/.05 = 85,000btu).  If it costs $3/sqft, that’s $46 per MMBtu, or about $5/gallon with a 80% boiler. Lots of assumptions here of course, but you get the gist. 
    Yes, but that using todays cost of fuel. What is oil going to be in 10, 20, 30 years?

    Using the same 5% Oil will go from $6 - $9.77. Roughly 50% increase!
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,004
    We won’t know future oil prices today, which is a good reason not to do it now. Also possible to hedge by buying some oil stocks. 
  • pecmsg
    pecmsg Member Posts: 3,536
    I'll bet its not going down by much over 10 years


  • leonz
    leonz Member Posts: 682
    jasonmm said:

    4 are baseboard heating and one is in-floor for a bathroom & shower.

    =================================================================

    Unless you willing to drill a deep geothermal well using
    the semi open loop method with a water furnace for water
    to water heat exchange it is a waste of time.

    If the bed rock is competent and tight it will hold water
    and you can drill down very deep to create cold water storage
    for heat exchange and cooling.

    For every 100 feet of drilled well depth you will have 1 ton
    of heating or cooling capacity.

    If the rock is not competent and tight you will need to mud
    drill the well to the full depth set casing to the full depth
    use a tremie pipe to pump sand mix cement into the well and
    use a wiper plug at the end of the drill string to force the cement
    up through the annulus of the well bore to the surface to seal
    the well bore and hold the water.

    If you have a stream or river with year round flow you could
    use an open loop method of heating and cooling with a
    water furnace which is the simplest way to do it.

    About shallow burial geothermal you need much, much, more
    ground for a shallow surface trench installation 6 feet deep
    with pipe runs 50 feet apart bedded in mason sand or concrete
    sand for a closed loop system.
    ====================================================

    You may want to think about using an overhead gravity hot water system for
    heating instead as it has so much more thermal mass from the water volume in
    the radiators and the steel or cast iron radiators.


  • Hot_water_fan
    Hot_water_fan Member Posts: 1,004
    I'll bet its not going down by much over 10 years


    I sure have no idea. Not my area of expertise. As the investment is evaluated over shorter time frames, the price/MMBtu goes up. Say you might move in 10 years - that makes the $3/sqft cost to go from R-20 to R-49 equivalent to paying $10/gallon today. Ouch! Maybe you can get some at resale, but I doubt it.